U.S. patent number 5,193,280 [Application Number 07/839,589] was granted by the patent office on 1993-03-16 for saw blades and method of making same.
This patent grant is currently assigned to Black & Decker, Inc.. Invention is credited to Brian K. Jackson.
United States Patent |
5,193,280 |
Jackson |
March 16, 1993 |
**Please see images for:
( Certificate of Correction ) ** |
Saw blades and method of making same
Abstract
A saw blade for a two-blade, contra-reciprocating saw has two
strips spot welded together. Teeth are formed by scallops cut along
an edge of each strip with lands between these scallops. Abrasive
grit, such as tungsten carbide chips, is brazed on the teeth except
on the sides of the teeth which rub against each other as the
blades reciprocate. The main cutting surfaces are the lands which
are longer on one strip than the other. The arrangement is useful
for cutting masonry and metal products and reduces stresses on the
blade.
Inventors: |
Jackson; Brian K. (Newton
Aycliffe, GB2) |
Assignee: |
Black & Decker, Inc.
(Newark, DE)
|
Family
ID: |
10690524 |
Appl.
No.: |
07/839,589 |
Filed: |
February 21, 1992 |
Foreign Application Priority Data
|
|
|
|
|
Feb 25, 1991 [GB] |
|
|
9103883.6 |
|
Current U.S.
Class: |
30/350; 125/22;
30/355; 30/369 |
Current CPC
Class: |
B23D
49/006 (20130101); B28D 1/127 (20130101) |
Current International
Class: |
B23D
49/00 (20060101); B28D 1/12 (20060101); B28D
1/02 (20060101); B26B 009/02 () |
Field of
Search: |
;30/369,348,350,355
;83/792,697,838,847,839,846,851 ;76/112 ;125/16.01,18,22 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0267311 |
|
May 1988 |
|
EP |
|
0275860 |
|
Jul 1988 |
|
EP |
|
0293941 |
|
Dec 1988 |
|
EP |
|
0361875 |
|
Apr 1990 |
|
EP |
|
0376128 |
|
Jul 1990 |
|
EP |
|
68684 |
|
Nov 1892 |
|
DE |
|
252251 |
|
Oct 1912 |
|
DE |
|
878477 |
|
Jun 1953 |
|
DE |
|
1230345 |
|
Dec 1966 |
|
DE |
|
1933230 |
|
Jan 1971 |
|
DE |
|
1964344 |
|
Jul 1971 |
|
DE |
|
2318378 |
|
Sep 1974 |
|
DE |
|
2443668 |
|
Mar 1976 |
|
DE |
|
3039063 |
|
May 1982 |
|
DE |
|
3236045 |
|
Mar 1984 |
|
DE |
|
3638404 |
|
May 1988 |
|
DE |
|
3724913 |
|
Feb 1989 |
|
DE |
|
3838844 |
|
May 1990 |
|
DE |
|
59-200766 |
|
Nov 1984 |
|
JP |
|
1299640 |
|
Dec 1978 |
|
GB |
|
Primary Examiner: Yost; Frank T.
Assistant Examiner: Payer; Hwei-Siu
Attorney, Agent or Firm: Dearing; Dennis A. Yocum; Charles
E. Bartlett; Edward D. C.
Claims
What is claimed is:
1. A blade for a contra-reciprocating two-blade saw including a
support guide for the blades, the blade comprising:
first and second strips secured together to form a single unitary
blade;
said first strip having teeth formed thereon;
grit particles adhered to the teeth on only one side of said first
strip;
said second strip being secured to said one side of the first
strip;
said second strip having teeth formed thereon in staggered relation
to the teeth formed on said first strip;
the teeth on said second strip having grit particles adhered
thereto;
said teeth comprising flat lands separated by curved scallops along
an edge of each said strip; and
the teeth having a pitch which is the same on each strip, with the
lands on the second strip being longer than the lands on the first
strip.
2. The blade as claimed in claim 1, wherein the lands have corners,
and a diagonal gap is provided between opposing corners of the
lands of adjacent teeth on the first and second strips.
3. A saw blade for a two-blade, contra-reciprocating saw, the blade
comprising:
two elongate strips of steel disposed side-by-side and spot welded
together;
an edge of each strip having teeth formed therealong, said teeth
being formed by scallops separated by raised flat lands;
abrasive grit particles adhered on said teeth, the teeth on one of
said strips having no grit particles on a side thereof facing away
from the other of said strips;
the land on said other of said strips being longer than the lands
on said one of said strips; and
the longer lands forming the main cutting surfaces of the
blade.
4. The saw blade of claim 3, wherein the teeth on said one strip
having the same pitch as the teeth on said other strip with the
lands of said one strip being staggered between the lands of said
other strip.
5. The saw blade of claim 4 wherein said grit particles are of a
size substantially the same as the thickness of the strips.
6. A saw blade, comprising:
two elongate strips disposed side-by-side and secured together to
form a single blade extending in a lengthwise direction;
a plurality of teeth spaced apart in said lengthwise direction
along a cutting edge of the blade;
said teeth being formed individually on both of said strips, the
teeth on each strip being formed by raised lands separated by
scallops;
the teeth on one strip alternating in said lengthwise direction
with the teeth on the other strip;
the land of the teeth of said one strip being longer than the lands
of the teeth of said other strip; and
abrasive particles adhered on the teeth of both strips.
7. The saw blade of claim 6, wherein said strips are secured
together by spot welding.
8. The saw blade of claim 6, wherein the teeth on said one strip
have a pitch which is the same as that of the teeth on said other
strip.
9. The saw blade of claim 6, wherein the size of said abrasive
particles and the thickness of each strip are substantially the
same.
10. The saw blade of claim 6, wherein:
the strips are secured together by welding;
the teeth on said one strip have a pitch which is the same as the
pitch of the teeth on said other strip;
the strips are of unequal height to form a shoulder extending in
said lengthwise direction along one side of the blade; and
the teeth of the greater in height of the two strips having no
abrasive particles adhered on a side facing away from the lesser in
height of the two strips.
11. The saw blade of claim 10, wherein the abrasive particles
comprise tungsten carbide.
Description
FIELD OF THE INVENTION
This invention relates to saw blades, and particularly to saw
blades for power saws of the type comprising a support guide for a
pair of blades reciprocating with respect to one another.
BACKGROUND OF THE INVENTION
Such saws are known and may include blades formed with integral
teeth which are ground and set to particular requirements. These
blades are suitable for wood and plastics but not for some
manufactured materials such as chipboard. Blades are also known,
for example from EP-A-0361875, which incorporate tungsten carbide
teeth set in the blade. These are suitable for cutting such
material as chipboard. Indeed this design has been found
particularly effective because alternate facing teeth on each blade
have chamfered faces firstly towards and secondly away from each
other. Those teeth chamfered towards one another urge the two
reciprocating blades together during their passage through the
material being cut, (and themselves very effectively cut material
by a scissor action as they pass one another) so that ingression of
loose cut material between the blades is minimised; while those
teeth chamfered away from one another rip out the inside of the
groove being cut in the material so as to make room for the blade's
passage through the material.
Although this design is very effective, even when they are employed
for cutting such masonry products as breeze blocks and the like the
life of the blade is nevertheless considerably shortened in this
sort of environment. In the first place tooth breakage sometimes
occurs and this may be caused for several reasons; for example, a
tooth simply hitting, and fracturing on impact with, a particularly
hard region of material being cut; or two teeth in scissor action
crushing between them a particularly hard grain. In the second
place, with such granular masonry material as breeze blocks and the
like, excessive wear occurs between the teeth, particularly where
the shape of the teeth causes them to be pressed together.
Thirdly, a possibly unrelated problem with the blades described in
the above-mentioned specification is beginning to come to light,
and which is probably caused by using the saw in such arduous
conditions. This problem is that, with this construction, blades
appear to be snapping on occasion adjacent their root in the saw.
This again may be caused by teeth impacting hard regions and the
blade buckling near its root where it is unsupported by the saw
blade support guide.
SUMMARY OF THE INVENTION
Thus it is an object of the present invention to provide a saw
blade which overcomes the above-mentioned disadvantages, or at
least mitigates their effects.
In accordance with this invention there is provide a saw blade for
a contra-reciprocating two-blade saw including a support guide for
said blades, the blade comprising a first strip having teeth formed
thereon and grit particles adhered on one side of said teeth and a
second strip secured against said one side of the first strip and
having teeth formed thereon in staggered relation to the teeth
formed on said first strip, the teeth on said second strip having
grit particles adhered thereto. Said grit particles may be tungsten
carbide chips or cubic boron nitride particles or such other
similar manmade hard material particles which are adhered to the
teeth by appropriate brazing or plating technique.
Preferably said teeth are flat lands separated by curved scallops
along the edge of said strips.
There is also provided a method of making a blade as defined above,
comprising the steps of: forming teeth in first and second strips
of metal; securing said strips together in side by side relation
with the tips of said teeth lying in substantially the same plane,
and in staggered relation one set of teeth with respect to the
other; masking one side of said first strip remote the second
strip; applying adhesive to the tips of the teeth exposed by said
masking; applying grit particles to said adhesive; and removing
said masking and curing said adhesive.
Preferably said adhesive is brazing paste, said grit particles are
tungsten carbide chips and said curing is heating sufficiently to
braze the chip particles to said teeth. Alternatively, the grit
particles may be such other manmade materials as cubic boron
nitride and said adhesive may be a plating medium.
Preferably said first strip is deeper than said second strip which
thereby forms a shoulder on said first strip for co-operation with
the edge of a slot formed in said support guide, said slot being
adapted to receive the first strips of two blades disposed side by
side with said second strips facing outwardly. Thus the absence of
grit particles on the side of the first strip remote from the
second strip means that the first strips of adjacent blades can
reciprocate with respect to one another without mutual
interference.
The two strips reinforce one another and so the blade as a whole
may be constructed longer. Moreover, since the teeth are flattened,
and are staggered with respect to one another on each strip, they
perform more of a grinding action when cutting so that there are
less longitudinal stresses on the blade. Consequently the
aforementioned problems of teeth, or even the blade, snapping
should be substantially al eviated. Also the grinding nature of the
material being cut will have less effect on the cutting surfaces of
the saw blades than occurs where teeth are meshing in a scissor
action.
BRIEF DESCRIPTION OF THE DRAWING
The invention is further described hereinafter, by way of example
only, with reference to the accompanying drawings, in which:
FIG. 1 is a side view of a power saw adapted to receive a blade
according to the present invention;
FIG. 2 is a perspective cut-away view of a blade according to the
invention;
FIG. 3 is a section on the line III--III in FIG. 1 showing a pair
of blades in a slotted guide;
FIG. 4a and 4b are views from either side of the blade of FIG. 2;
and
FIG. 5 is a partial bottom view of the pair of blades of FIG.
3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1, a power saw 10 has a pair 11 of blades 1 supported in a
slotted guide 2 connected to a housing 3 for a motor. The motor
drives the blades 1 in contra-reciprocation with respect to one
another. The saw has a handle 4 and switch 5 and a further,
steadying handle 6.
Each blade 1 (see FIGS. 2 and 3) comprises two strips of steel 12,
14 secured together, the first strip 12 being wider than the second
strip 14 to form a shoulder 16. Two blades 1 are supported in the
guide 2 which includes a slot 18 to receive those parts 20 of each
strip 12 which extend beyond shoulder 16.
The shoulder 16 bears on the ends of the slot 18. Each blade 1, at
its housing end 24, is provided with a reinforced threaded eye 26
which is engaged by a correspondingly threaded driving pin (not
shown) driven by the motor. At its free end 30, each blade 1 has a
slot 32 through which a pin 34, releasably secured in the guide 2,
passes, so as to support the blades 1 (with freedom to reciprocate
along their axes) at their free ends.
Teeth 42, 44 are formed on the adjacent edges of each strip 12, 14.
The teeth 42, 44 have the same pitch and alternate with respect to
one another. The teeth 42, 44 are formed by scallops 46, 48
separated by lands 52, 54. The scallops 46 in the strip 12 are
deeper, and have a larger radius, than those of the strip 14, so
that the lands 54 are longer than those on the strip 12. This is
because the lands 54 are the main cutting surfaces of the blade
pair 11. This also ensures that there is a diagonal gap 43 between
facing corners of adjacent teeth on either strip, for reasons
explained further below.
All the teeth 42, 44 are provided with a coating of grit particles
(shown on only some of the teeth in the drawings). This is achieved
by applying to the teeth a brazing paste and dipping them in
tungsten carbide chips. Subsequent heating to about 1000 C bonds
the chips to the teeth in a known process and results in an
abrasive coating to the lands and sides of the teeth 42, 44. Other
particles and other adhesive techniques could be employed.
However, the sides 50 of the strips 12 which face one another when
positioned in the saw 10, (which sides are remote from the strips
14) bear against each other during their contra-reciprocation in
the guide 2. Consequently the sides 53 of the teeth 42 on that side
50 of strips 12 cannot have grit applied to them, otherwise the
teeth 42 on one strip 12 would bind with those on the other strip.
Thus prior to the application of brazing paste, masking tape is
applied to the strip 12 along side 50 up to the level of lands 52.
Thus when the teeth 42, 44 are dipped in the brazing paste the
sides 50 of the teeth 42 are masked. The masking tape is removed
before the heating step, either before or after the grit is
applied. Other means of masking that side of the strip 12 could be
employed.
The grit particles are of a size substantially the same as the
thickness of the strips 12, 14. This results in a degree of
overlap, in the transverse direction with respect to the length of
the blade, between teeth 42, 44 as shown in FIG. 5. The diagonal
gap 43 is provided to allow grit to occupy the space between
opposing teeth 42, 44 on the blade 1. Also, the outer grit coating
on teeth 44 stands somewhat proud of the side 51 of each strip 12.
Thus during the sawing action the blades 1 are pressed against one
another and the arrangement of the alternating teeth 42, 44
simulates a wave action down the length of the blade which assists
this pressing together of the blades. Moreover, with the bottom
edge 60 of the blade pair 11 providing a largely continuous
surface, the cutting action is primarily a grinding process, very
effective with granular masonry material such as breeze block. The
scallops 46, 48 assist clearance. Dust getting between the blades 1
will always be a problem, but it does not affect the cutting
surfaces o cutting action of the blade. There is of course a
scissor action between teeth 42 but this is not part of the cutting
action of the blade arrangement.
While the blades are primarily designed for cutting masonry
products, it can also be used to good effect on metals, although in
this latter respect a long blade is not required.
Finally, the nature of the cutting action of the blades 1 is itself
responsible for a reduction of the longitudinal stresses on the
blade. Nevertheless, there is the unavoidable scissor action
between the teeth 42 which could still trap hard particles between
them. However, the teeth 42, 44 are not themselves hard, being
formed from strip steel, and so will absorb impacts without
shattering. Moreover, the strip 14 serves to reinforce the strip
12, particularly at the root of the blade near its end 24 where it
exits the slot 18 and is laterally unsupported. It is here that
blade breakage has sometimes occurred in the past.
The two strips are conveniently spot welded together, at about
every third tooth, as shown at 63 in FIG. 4.
* * * * *